Field of the Invention
The present invention relates to a display apparatus that is capable of determining a format or a type of an analog video signal.
Description of the Related Art
There is known an image display apparatus that is provided with an analog video input terminal and that supports types of analog video signals having different horizontal synchronous frequencies/vertical synchronous frequencies. Such an image display apparatus determines a characteristic value (e.g., a horizontal synchronous frequency, a vertical synchronous frequency, a horizontal resolution, and a vertical resolution) of an input analog video signal, and converts the input analog video signal to a digital signal at a sampling frequency in accordance with the determination result. Japanese Patent Laid-Open No. 10-91127 describes a video signal determining technique for determining the most appropriate format by comparing a characteristic value of a video signal stored in a memory with a characteristic value of an input analog video signal.
As there is an increasing variety of analog video signals, it is becoming difficult to differentiate among analog video signals only by a vertical resolution, a horizontal resolution, or a vertical frequency. Among video signals of 1280 pixels×1024 lines (60 Hz), for example, there are video signals that have the same vertical resolution and the same horizontal resolution but have different blanking periods or different quantization clock timings. In a case in which video signals differ only in terms of their blanking periods or quantization clock frequencies, it is difficult to appropriately estimate video formats through the technique described in Japanese Patent Laid-Open No. 10-91127. When the video formats are estimated incorrectly, a deviation in the angle of view, a missing view angle, or an image disturbance may occur.